There has been known a manufacturing method of a semiconductor device includes a wire-bonding process for bonding bonding balls to electrode pads.
In accordance with the recent narrowing of pitch of electrode pads, a technique where the shape of the bonding balls is changed from round to oval has been suggested in, for example, Japanese non-examined laid-open patent publication No. Hei 10-56030 (page 2).
In a wafer test conducted prior to wire-bonding, a process for pressing a probe against electrode pads, i.e., probing, is carried out. For this reason, probe marks appear in the electrode pads after the wafer test. Since a part of the bonding ball directly upon a probe mark does not contribute to the bonding, there is a problem that the area of bonding of the electrode with the bonding ball becomes smaller compared to the bonding area when there are no probe marks.
Further, an offset occurs in the form of the bonding surface of the surface of the electrode pads with the back surfaces of the bonding balls along the shape of a probe mark. Accordingly, as shown in FIGS. 7A and 7B, during the loop pull test conducted after the wire-bonding, the part of the bonding ball 2 directly upon the probe mark 1 is lifted first, and a momental force occurs to the bonding ball 2. Consequently, there is a problem that the electrode pads 3 peel off during loop pull test. FIG. 7B is a cross-sectional view taken along line B-B′ of FIG. 7A.
Moreover, as shown in FIG. 8, in the case where a plurality of probe marks 1 exist in an electrode pad 3, small-area junction parts 5 exist in the gap between the probe marks 1. Also in this case, tensile stress is applied to the small-area junction parts 5 during loop pull test. For this reason, there is a problem that the electrode pads 3 peel off during loop pull test due to stress concentration.